size

[truckboss]

hi guys, been lurking for a time,now a ?.i have a rcbs 44 mold and have been trying different alloys temps etc.what will make the size change .i get anywhere from .4305 to .4285?my grove is .430.thanxs,brian.

[fourarmed]

Hi Brian, welcome to the boola boolit site. The main thing that controls fillout in a mold is surface tension of the molten alloy. The lower the ST, the bigger the boolit, other things being et cetera. Probably the largest factor affecting ST is tin content. The more, the better, within limits. Beyond a few percent, it doesn't help much. Temperature has a significant effect on the ST of most liquids, so I assume it does on lead alloys, too. However, cooling contraction and crystallization at different temperatures play a part, so I don't think the relationship is a simple one.

[leftiye]

More antimony makes a boolit shrink less when cooling. Adds about aa thou. to boolit dia.. I'd add the tin too as it coats the antimony crystals and makes them less abrasive (plus helps with fillout as mentioned by F. A. above).

[truckboss]

thanks for the replys.yeah about 75% lino to range lead got me almost .431,75% range lead 25% lino got me about .428,does that seem like to much of a spread?

[fourarmed]

I have seen variations of around a thousandth while experimenting with a particular .30 caliber mold, so that much variation with a .44 mold doesn't seem outlandish.

[VTDW]

Most of us like to shoot a boolit about .002 over bore size so you are pretty good to go.

Dave